There are (2) tasks at hand...move a cylinder (pneumatic or electric or hydraulic?), move the cylinder to a position. The 2nd task will require position feedback and closed-loop control. Both tasks are highly mechanical for specification (the controls guys take care of the programming and wiring). There is no way to concept the controls with a questionable mechanical concept.
What is the specification for position accuracy? How precise must the cylinder final destination be held to (+/- fractional thousandths, +/- an inch).
What is the specification for cylinder speed? How much time is allowed for the cylinder position to be changed.
What is the specification for total load to be moved?
Reed switches are often used in cylinders for general cylinder actuation feedback. However, these buggers are a pain to adjust with high accuracy. Reed switches are binary...they only tell you if you are at Position A or B. If you budget is low and the specification is Low Accuracy, a cylinder with multiple reed switches per the customer location is an option.
If your budget is higher and the specification is for High Accuracy, a servo cylinder is an option (servo-pneumatic or servo-hydraulic). Such as a Festo servopneumatic system. https://www.festo.com/cms/nl-be_be/16425.htm
Parker, Festo, IAI...good places to start

The dated PowerFlex 4M has an Ethernet-type RJ45 port, but this is a RS-485 port (DSI). Ethernet/IP was not commonly utilized when the 4M was rolled out.
If you can connect to your system without Ethernet/IP, programming is done via the keypad.
If you want to physically connect to the drive, you will need either DriveExplorer or DriveExecutive and a serial converter (#22-SCM-232). Also known as "The Anaconda". http://literature.rockwellautomation.com/idc/groups/literature/documents/um/22comm-um002_-en-p.pdf
You can add a DSI interface module to your panel to convert the 4M RS-485 (DSI) port to Ethernet/IP. http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1769-um013_-en-p.pdf
Or you can add an Ethernet/IP communication board to the PowerFlex 4M VFD, the #22-COMM-E. http://literature.rockwellautomation.com/idc/groups/literature/documents/um/22comm-um004_-en-p.pdf

Allen-Bradley does have a brochure for the PF 755 utilized for material handling/crane applications. However, the literature does not fully disclose "anti-sway" ability. If you are talking material handling/anti-sway control, "lower cost" often is a recipe for a problem.
http://literature.rockwellautomation.com/idc/groups/literature/documents/br/pflex-br009_-en-p.pdf
Magnetek, a material handling controls/equipment manufacturer, does have an anti-sway control solution. https://www.magnetekmh.com/Products/AC%20Drives/IMPULSE%20AC%20Drives/Sway%20Control%20System%20Series%202
ABB has more of a refined material handling/anti-sway solution. https://new.abb.com/drives/media/crane-control-solutions

It has been a few years, but I ran into a situation with the K300 continuously generating an E06-Hardware Overtravel fault that would not go away. The fix per Rockwell...add 1.5K 2W resistors in parallel with each extreme limit input (stray electrical noise sensed as an extreme limit input ON condition).

Usually, a cross reference will help you find the culprit (like 2 pieces of code controlling the same parameter). However, with UDTs bundled into an AOI, is is very easy to have this situation. If anyone has used the open-source PackML template (which Collins may be working with) then you know what I am talking about. It is very possible to "walk on" a tag within the AOI. I wrestled with the very same type of situation for a long time, and ended up re-writing the whole program without the pain-in-my-butt PackML template.

Upfront motion application design questions: How will this master-slave relationship work, overall? The scope of operation is not defined. What is your motion resolution accuracy specification? Resolution accuracy spec may or may not be capable. How is the hydraulic cylinder controlled? In order to slave a K300 servo controller, commanded with motion instructions, to a hydraulic cylinder, the cylinder control will need to be via a motion command, also.
Once the scope of operation is known, then research the motion commands needed. Pull down the Logix/Studio Motion Instructions Reference Manual (Chapter 2, Motion Move Instructions). From what I read...MAG (motion axis gearing) is probably the ticket. Master (hydraulic cylinder control output with encoder position feedback input) is slaved to K300 servo motor. In this fashion, whenever the Master is commanded, the Slave is commanded per the gear ratio.
After you have scope and motion figured out, then it is onto determining the encoder feedback. There are a number of encoder types for different applications. Refer to the attached.
Understanding Encoders.pdf

You will need screenshots to fully express your situation. I suspect your issue is with the scripting of register addresses; your SLC-500 PLC name is what is shown in RSLinx and that is what will be [shortcut] in RSView ME.
For migrating a PV550 to a PV700, if the previous PV550 HMI application required operators to acknowledge all alarms (otherwise how would the alarms go away), the new PV700 application should do the same. Otherwise you will be modifying the behavior of the machine.

Ideally, a one-to-one PLC program conversion with identical HMI screen layout/functionality is probably the objective. Same functionality, updated equipment - no enhancements.
Request a drawing of the whole control system. There could be communication modules that interface with other equipment (remote I/O racks, DeviceNet to VFDs, etc.). You need to be 100% sure of everything controlled by this PLC.
You will need the latest PLC program. Do you have PLC-5 programming software (i.e., RSLogix 5 or AI)? The complexity and functions that are in the PLC code will dictate which platform to upgrade to. A CompactLogix 5370 L1-L2-L3 controller may be a good choice, but features utilized may force you to upgrade to a ControlLogix.

With Fanuc robots and Ethernet/IP to an external controller, the key is the I/O stack. The robot may communicate Ethernet/IP (the HOW), but it utilizes a stack of I/O (the WHAT) for the heart of the communications.
Work Instruction - Fanuc Robot System Startup.docx
Work Instruction - Omron PLC Ethernet-IP With Fanuc Controller.doc

This is where Sick's literature will drive your configuration, it is not a Rockwell/Allen-Bradley decision. I have seen Generic Ethernet module configurations of Type INT or SINT; the hardware manufacturer (Sick) will specify what works for them. Then you need to know the number of input & output words and the instance numbers.
I found a Sick blog that suggests...Type-SINT, input instance-105, size-124; output instance-100, size-4; Config instance-1, size-0. In the Connection tab, turn ON Use Unicast Connection Over Ethernet/IP. http://sickusablog.com/easily-obtain-inspector-vision-sensor-data-ethernetip/

Great topic, something I had wondered about using for years but never got around. Page 28 digs into it; tags configured that you can monitor in your code. https://www.rockwellautomation.com/resources/downloads/rockwellautomation/noa/RAOTM%20Lab%20Manuals/L02-manual.pdf

Specifically which faults are you getting when trying to energize the VFD? Let the drive display cycle through ALL existing faults.
Install Connected Components Workbench, get connected to the problem VFD, and go online to dig further into the details of alarm history.
Are you getting F041 (Phase U-V) & P042 (Phase U-W) & P043 (Phase V-W)? If you are not getting all 3 phase shorted faults, the VFD may be telling you that this fan motor has failed. However, if you are only getting one phase shorted fault, and you have metered the windings and did not find a line-to-line short, then this fan motor needs to be meggered (with a motor megger - tests the motor windings).